Hi @CindyBryan,
I work in higher education and specifically in my institution's Department of Online Learning, which is separate from our IT Department. With that said, while Canvas could do what you are looking for, I think as you go about using it for this purpose, there will be problems.
As said by @james_whalley and @Gabriel33, the Canvas LMS can technically do this but it (because of how it currently is designed) has its limitations in the Canvas Inbox (from my perspective and already mentioned, primarily because it does not support format, embedded images, and there can be user account quota problems). There are work arounds but they are not what I would recommend for an entire institution.
I think what you are looking for is a mix of things: (1) a "portal" of some sort that serves as a hub for accessing other systems/websites and allows for different roles/permissions and (2) a communications platform that allows faculty and administration to reach out (either as announcements for everyone or one-to-one) to different roles.
I hope that our replies helped you to think about this a little more and differently.
-Doug